Although electromagnetic induction heating is widely utilized in fields such as heat treatment, surface treatment, and melting, etc. metal processing, this type of heating has also been used in recent years for the continuous heating of fluids such as gases, liquids, etc.
A method has been proposed for electromagnetic induction heating of a fluid by heating a round metallic rod using an electromagnetic induction heating coil. The circular rod is mainly heated by the surface wave effect so that the outer periphery of the circular rod is heated. A fluid is made to flow at the periphery of the circular rod along the rod length axis. The fluid flows within this apparatus through a flow passage (circular rod) that is heated by electromagnetic induction heating, thereby indirectly heating the fluid. This method is deficient in that the overall heating efficiency is largely determined by the efficiency of heat transfer between the flow passage and the fluid.
It is therefore proposed that a metallic heating element be inserted into a flow passage that is constructed from a non-electrically conductive material, and that this metallic heating element be heated by electromagnetic induction. This proposed apparatus utilizes the direct heating method to raise the heating efficiency. For example, it has been proposed that a star-shaped heating element be placed within the fluid flow passage, and that a heating coil surround the perimeter of the fluid flow passage. A starshaped heating element is used since the heat transfer surface area is increased, and since the surface greatly increases that is heated by the surface wave effect. However, starshaped heating element surface area heating is limited, thereby resulting in a limitation upon the degree of improvement of heating efficiency.
Therefore the same inventors have proposed a great increase in the heat transfer surface area, the area that is both heated by electromagnetic induction and that serves as the heat exchange surface. Specifically, a heating element is contained within a fluid flow passage. This heating element is a layered component, consisting of many metallic plates, constructed so as to be electrically conductive. Electrical current vortices occur throughout the metallic plates that comprise the layered component. Since the metallic plates are electrically in contact with one another, the central region is more readily heated than the layered component peripheral region. This results in a method to enhance the electromagnetic heating surface wave effect. Per this heating method, the surface area of the layered component is greatly increased, and the efficiency of heat transfer from the heating element to the fluid in raised by nearly 100%. It becomes possible to create conditions for ready control of temperature.
Moreover, turbulent flow and mixing of the fluid are made to occur within the fluid flow passage within the layered component (the above-mentioned heating element). This therefore assures that the fluid within the layered component is uniformly heated. In contrast, a heating element is also proposed that causes a controlled flow through a fluid flow passage other than through this layered component.
However, by the use (as a heating element) of a layered component that has a fluid flow passage that causes mixing and turbulent flow within the fluid, heat transfer efficiency was greatly improved between the heating element and the fluid. It then becomes necessary to improve the efficiency of electrical power transfer to this heating element. In other words, the advantages of a layered component heating element began to appear upon combination of this type of heating element with an efficient high frequency electrical current generator. The electromagnetic induction fluid heating apparatus was realized.
Therefore the goal of this invention is to provide an advantageous combination of a high frequency electrical current generator and a layered component heating element.